Apparatus for continuous vacuum deposition

ABSTRACT

A vapor deposition apparatus is provided wherein a workpiece strip is passed over a rotatable masking wheel within a vacuum environment. The evaporation source and material to be evaporated and deposited upon the strip is located within the perimeter of the masking wheel. It is deposited upon the strip as it passes along the masking wheel. The masking wheel consists of two or more parallel, and independently mounted rings which are axially aligned and axially adjustable for altering the gap between the rings, and hence the width(s) of the material deposited on the workpiece strip.

United States Patent Krumme et al. 1451 May 29, 1973 1541 APPARATUS FOR CONTINUOUS 3,041,194 6 1962 ROSen C131. l ..118/301 x .VACUUM DEPOSITION 3,102,046 8/1963 Bushey ..1 18/301 x 1 1 3,205,855 9 1965 A l! ..118 49 [75] Inventors: John Frederick Krumme, Woodside; 3 206 322 941965 i 1 18/4; X 130mm Thomas Fwd, Menlo Park 241,519 3/1966 Lloyd ..118/49 both Ofcalifi 3,511,212- 5 1970 Bums..... 118/49 3,585,965 6/1971 Kaspau ..118/48 [73] Asslgnee' i' Incorporated Redwood 1,785,833 12/1930 Keck ..118/504 ux Clty, Calif.

[22] Filed: Dec. 1, 1971 Primary Examiner-Morris Kaplan 1 Attorney-Karl A. Limback, George (I Limbuch [21] Appl' 203813 11nd John P. Sutton et al.

52 us. Cl. ..118/49 [571 ABSTRACT [51] .Int. Cl ..C23c 13/10 A vapor deposition apparatus is provided wherein a [58] Field of Search ..l,l8/4849.5, workpiece Strip is passed Over a rotatable masking 0 5 3011406; 1 38 wheel within a vacuum environment. The evaporation source and material to be evaporated and deposited upon the strip is located within the perimeter of the [56] References cued v masking wheel. It is deposited upon the strip as it UNITED STATES PATENTS passes along the masking wheel. The masking wheel conslsts of two or more parallel, and independently 1,551,850 9 1925 Schm'idrner et a1 ..1l8/49X mounted rings w i h ar axially aligned and axially 52 73:? g adjustable for altering the gap between the rings, and e elmer... 2,707,162 4 1955 Fries ...118/49 x i 5 0f the materal depwted the 2,768,098 10/1956 l-loppe ...ll8/49X P162e 8/1960 McGraw, Jr ..118/49 11 Claims, 15 Drawing Figures PATENTED MY 2 9 I973 SHEET 1 OF 5 DONALD T. FORD ATTORNEYS PATENIEbHf.Y29Y.-5 3,735,728

SHEET 3 [IF 5 JOHN F. KRUMME DONALD T. FORD ATTORNEYS INVENTORS PATENTH EH29 I975 mm n []F 5 E S D &ll0 U Nm El. v T NE I L NA UN 00 JD ATTORNEYS APPARATUS FOR CONTINUOUS VACUUM DEPOSITION BACKGROUND OF THE INVENTION The present invention relates to improved apparatus for continuous vacuum deposition, and in particular to improved apparatus for depositing a continuous stripe or pattern of evaporated material on a workpiece strip which is continuously conveyed past the point of deposition.

Vacuum deposition is a well-known process wherein a material, typically a metallic material is deposited upon a workpiece or object material. In some cases the workpiece is an insulating or organic material and in other cases it is a metallic material. As the name implies, the deposition occurs in a vacuum environment.

To evaporate the source material for deposition upon the workpiece, one of a number of well-known techniques can be used. For example, the source material can be bombarded with high energy electrons which cause the source material to be heated and hence evaporated when evaporation temperature is reached. Alternatively, the source materials can be heated, by, for example, passing large currents through the source material to heat the same, which results in evaporation of the source material. Both of these techniques require a vacuum environment for their operation.

In one prior art vacuum deposition apparatus, the workpiece material, comprising a strip or web of material, which is stored on a payoff reel or spindle, is passed over a masking wheel and onto a takeup reel or spindle. The source material is located within the perimeter or circumference of the masking wheel and provides a source of evaporated material which is radially projected through perforations in the wall of the masking wheel onto the workpiece strip. The perforations define deposition patterns on the workpiece strip.

In other systems, the pattern of deposition is formed by the use of a second or masking strip which passes along with the workpiece strip between the latter and the deposition source. I

Prior art vacuum deposition devices, such as those described above, are unsatisfactory for many applications. First, it is often impossible or very difficult to adjust the dimensions and parameters of the stripe or pattern of material being deposited on the workpiece strip. Thus, for example, in applications wherein a stripe of source material is deposited on a passing workpiece strip, it is often desirable or necessary to be able to quickly and easily vary the width of the strip.

Secondly, in many applications, such as where a masking strip is used with and passes with the workpiece strip, it is important that the workpiece and masking strip be very accurately aligned. In particular, this is required in the construction of lead frames for integrated circuit fabrication. Lead frames, to which integrated circuit chips are electrically and mechanically connected and held are typically made of low expansion materials such as ASTM Alloy F15, ASTM Alloy F30, or pure nickel. The wire leads from the integrated circuit ships, typically are ultrasonically bonded to the lead frame structure.

To construct a lead frame, it is necessary to deposit a coating of another material on a part of the workpiece strip. This is accomplished by the vacuum deposition apparatus described above and which forms the subject matter of the present invention. The configuration of the coating on the workpiece strip varies from application to application. In some cases, it is desirable to have a continuous stripe on the workpiece strip. In other cases a particular pattern, such as a' series of rings is required. This all depends upon the nature of the integrated circuit chip and the desired configuration of the lead frame.

In subsequent fabrication steps, parts of the workpiece strip are cut away to form the lead frames lead. This process, typically carried out by mechanically stamping out the desired lead frame pattern, results in the coating 'material forming the tips of each of the lead frames. It is to these tips that the integrated circuit leads are ultrasonically bonded to the lead frame.

The primary reason for the use of the coating material is to provide a material on the lead frame which has an identical or similar properties to the materials used for bonding to the integrated circuit chip or substrate. Typical coating materials include aluminum, and BT braze alloy (72 percent silver, 28 percent copper).

SUMMARY OF THE INVENTION It is therefore an object of the invention to provide vacuum deposition apparatus in which the dimension parameters of the deposited material are easily variable.

Another object of the invention is to provide vacuum deposition apparatus wherein the dimensions and shape of the deposited pattern on the workpiece strip is very accurately controlled and gauged.

Another object of the invention is to provide a vacuum deposition apparatus which provides multiple stripes or pattern sequences on a moving workpiece strip.

In accordance with the present invention, the width of the stripe or pattern deposited upon the workpiece strip is made variable by use of a masking wheel which comprises a pair of independent, parallel and axially aligned rings which are arranged side by side to form a narrow space or gap therebetween which defines the maximum width of the stripe or pattern to be deposited upon the workpiece strip which passes over the masking wheel. To permit variation in the maximum width of the masking stripe or pattern, the rings are axially adjustable.

To reduce the amount of material deposited upon the underside of the rings forming the masking wheel, a shield having a slot therein to allow passage of the evaporated material therethrough, is secured to the rotatable masking wheel. Since the shield rotates with the masking wheel the excess evaporated material is uniformly distributed along the shield which reduces the buildup of excess evaporant at any one point along the rotating shield.

To insure the proper alignment of the workpiece strip, particularly where a separate masking strip is transported along with the workpiece strip, indexing means are provided. In one embodiment, indexing teeth are provided along the surfaces of the rings forming the masking wheel. These teeth cooperate with alignment perforations located along the edges of the workpiece strip and the masking strip. This arrangement provides for very accurate alignment and insures dimensional uniformity during the deposition process.

In accordance with another aspect of the invention, multiple rings are used to form the masking wheel when it is desired to provide more than one stripe or pattern on the workpiece strip.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view of a vacuum deposition apparatus in accordance with the invention.

FIG. 2 is a perspective view of the masking wheel, shown in FIG. 1, incorporating the present invention.

FIG. 3 is a cross-sectional view of the masking wheel of FIG. 1 taken along a direction indicated by the arrows 3-3'in FIG. 1.

FIG. 4 is a cross-sectional view of the masking wheel of FIG. 1 taken along a direction indicated by the arrows 44 in FIG. 1.

FIG. 5 is a topview of a portion of the masking wheel shown in FIG. 4 and taken in the direction indicated by the arrows 5-5 in FIG. 4.

FIG. 6 is a cross-sectional view of a masking wheel of FIG. 1 taken in a direction indicated by the arrows 66 in FIG. 1.

FIG. 7A is an illustration of a workpiece strip, FIGS. 78 and 7E illustrate the workpiece strip after vacuum deposition, FIGS. 7C and 7F illustrate the workpiece strip after the lead frame pattern has been formed and FIG. 7D illustrates one example of a masking strip.

FIG. 8 is a cross-sectional view similar to FIG. 4 of another embodiment of the invention using multiple rings to form the masking wheel.

FIG. 9 is a cross-sectional view similar to FIG. 5 showing a multiple ring masking wheel.

FIG. 10 is an elevational view incorporating the present invention of vacuum deposition apparatus utilizing a mask strip in addition to the workpiece strip.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1 of the drawings, vacuum deposition apparatus 10 includes a vacuum chamber 11, a payoff reel or spindle 12, a takeup reel or spindle 14, a masking wheel 16, and deposition source material 18 which, by suitable means, is evaporated and directed to the deposition area. The source material 18 is evaporated by any suitable means, such as bombarding the source material 18 with electrons from an electron beam device 19. Electron beam device 19 can, for example, be of the type manufactured by Airco-Temescal Corp., Berkeley, California, and referred to as their electron beam evaporation system.

Coiled on the payoff reel 12 is a workpiece strip 20 which is threaded and directed to the masking wheel 16 by suitably mounted guide roller 22. The strip 20 passes along the outside perimeter or circumference of the masking wheel whereupon it is returned to the takeup reel 14 after passing over a pair-of water-cooled rollers 24 and 26 and a guide roller 28.

Referring additionally now to FIGS. 2 through 6, the masking wheel 16 comprises a pair of independently mounted, rings or wheels 30 and 32 which are arranged parallel to one another along the same axis. As will be explained these rings are axially adjustable with respect to each other. The gap or space 34 located between the two rings 30 and 32 defines the maximum width of the stripe or pattern which is deposited upon the workpiece strip 20 as it passes over the masking wheel 16 above the source of evaporated material 18. The rings 30 and 32 forming the masking wheel 16 are rotatably mounted within a circular support frame 36 which comprises a pair of annular support rings 38 and 40 which are rigidly mounted by means of a support bracket 42 to a base member 44.

Referring particularly to FIG. 3, a shutter 46 is mounted to the vacuum chamber wall 12 by means of a shutter support member 48 which is connected by an end member 50 to a way 52. The shutter 46 is driven to a position above and adjacent to the evaporation source 18 during the initiation of a deposition process. Its purpose is to prevent the evaporated material from reaching the workpiece strip until the source 1 18 is sufficiently warmed up and has achieved the required evaporation rate.

The way is movably mounted by means of a way mount assembly 54 which comprises a support member 56 to which are mounted four guide rollers 58. The shutter is moved in and out of the interior of the masking wheel 16 by a drive wheel 60 which frictionally engages the way 52. The shutter support 48 and the way 52 extend through a hole 62 formed in the vacuum chamber wall 12.

To reduce the building up of unwanted source-material on the underside of the rings 30 and 32, a rotating shield 64 is provided. The rotating shield comprises a first shield 66 and a second shield 68. Referring in particular to FIG. 6, the shields 66 and 68 are secured, respectively, to rings 30 and 32 by means of mounting brackets 70. The rotating shield 66 and 68 are thermally and mechanically isolated from the rings 30 and 32 by means of ceramic spacers 72. The bracket 70 and spacers 72 are connected with the rings 30 and 32 by suitable mounting means such as a bolt 74.

The rings 30 and 32 forming the masking wheel 16 are rotatably held and maintained by means of three guide roller sets 76 and a pair of support roller sets 78. Referring particularly to FIGS. 4 and 5, each guide roller set 76 comprises a pair of guide roller bearings 77 for each of the rings 30 and 32 respectively. Each pair of roller bearings 77 are inclined 90 to each other and at an angle of approximately 45 relative to the top surface of the rings 30 and 32. Rings 30 and 32 are each provided with a raised guide portion 80 which include two beveled portions 82 inclined at 45 to the top of the rings 30 and 32. As may be seen, the roller bearings 77 cooperate with the beveled portions 82 to guide and positively maintain rotating rings 30 and 32.

Each pair of roller bearings 77 is mounted by means of a bearing support 84. Each of the bearing supports 84 is slidably mounted on an axil 86 which in turn is mounted to the support rings 38 and 40 respectively by suitable mounting means such as bolts 84.

By adjusting the position of the bearing support 84, and hence the roller bearings 77, it is possible to adjust the distance or gap 34 between the two rings 30 and 32. Once the roller bearings 77 are moved along the axils 82 to the proper position to obtain the proper gap 34,

the bearing support member 84 is locked into place by means ofa combination of a thrust washer 86, retaining ring 88 and a bolt 90 which is secured in place by means of a suitable fastener such as a set screw 92. With this arrangement it is very easy to adjust the width of the gap 34 defined by the two rings to enable stripes of varying widths to be deposited.

Details of the support rollers 78 are shown in FIG. 6. A support roller 78 is provided for each of the rings 30 and 32 at two points near the bottom of the masking wheel. The support bearings 78 are each supported on a'shaft 94 which in turn is secured between the support frame members 38 and 40. The support rollers 78 are held in place by means of thrust washers 96. The support rollers 78 support and ride upon the top surface of the rings 30and 32.

The workpiece strip is supported by the rings and 32 within a recessed portion which is formed by notched portions 98 and 100 formed on rings 30 and 32 respectively.

The workpiece strip 20 is shown in FIG. 7A prior to the deposition process. After the deposition a stripe 23 results upon the strip 20. The width of the stripe 23 is determined by the size of the gap 34 between the rings 30 and 32.

FIG. 7C shows the workpiece strip 20 after the lead frame has been stamped out. Formed by the stamping process are a plurality of conducting arms 25 having tips 27 coated with the deposited material.

FIGS. 8 and 9 illustrate an alternate embodiment of the invention wherein multiple rings are provided to form the masking wheel thereby enabling multiple stripes or patterns to be deposited upon the workpiece strip 20. More particularly, the embodiments of FIGS. 8 and 9 include three rings, 100, 102 and 104 which, like the previously described embodiments, are aligned parallel with one another and are movable axially to provide an adjustable gap width 106 between rings 100 and 102 and a space or gap 108 between the rings 102 and 104.

In the manner of the previous embodiment, shields 110, 112 and 1 14 are attached and secured to the rings 100, 102 and 104 respectively to reduce the amount of buildup of deposited material on the rings. 7

The workpiece strip 20 extends from the inside edges of rings 100 and 104 and across the entire width of ring 102. As a result, the bearing set 76 for the middle ring 102 must be eliminated from the top of the masking wheel because of the travel of the workpiece strip 20 over the top of the masking wheel. Since it is necessary to guide and position the middle ring 102, the roller bearing set for that ring (not shown) must be located at a position along the masking wheel where the workpiece strip does not contact the masking wheel 16. In general, this means that this roller bearing set must be provided along the lower portion of themasking wheel circumference.

Because the strip covers the entire top surface of the middle ring 102 at and near the point of deposition it is not possible to have a raised guide portion 80 as with the outer rings. Instead, a recessed or grooved area 81 provides a guide for the bearing.

Since the workpiece strip does not travel along the bottom of the masking wheel 16 there is no problem in providing an additional support roller for the middle ring 102. Thus, as may be seen by reference to FIG. 9, support rollers 120, 122 and 124 are provided to support the rings 100, 102 and 104 respectively. Note that the middle support roller 102 is guided by the recessed portion 81.

In the embodiment of FIGS. 8 and 9 use of the three rings 100, 102 and 104 to form two gaps 106 and 108 means that two stripes or patterns of deposited material are possible. It should be understood that with additional rings,'even greater numbers of stripes or patterns may be deposited on one workpiece strip. In particular, if N stripes are required, N+l rings are used to form the masking wheel.

As described earlier, it is sometimes desired to provide a pattern of deposited material upon the workpiece strip rather than a continuous stripe. FIG. 10 illustrates schematically a system for achieving this result. Workpiece payoff reel passes a workpiece strip 132 over masking wheel 134 and onto takeup reel 136. The masking wheel 134, preferably, is of the type described above.

Aligned and in contact with the workpiece strip 132 is a mask or stencil strip 138. This mask or stencil is provided with perforations of the size and configuration which is desired to be deposited upon the workpiece strip. The mask 138 is fed out from a mask payout reel 140 through a pair of support rollers 142 which bring the workpiece strip 132 and mask 138 into contact with one another. Thereafter they pass over the masking wheel 134 where the combination of the mask/workpiece strip is exposed to the evaporation source material 144. After leaving the masking wheel 134 the mask is separated apart from the workpiece strip and is taken up on the mask takeup reel 146 after passing by support rollers 142.

To insure that the mask and workpiece strips are properly aligned, both rings of the masking wheel 134 are provided with a series of cogs or teeth 146 which are located periodically around the circumferences of the respective rings forming the masking wheel.

A section of the workpiece strip is shown in FIG. 7A. The workpiece strip shown in FIG. 7A is provided with index holes or perforation 150, along the edges of the stripe. These holes cooperate with teeth or cogs 21 (FIG. 4) located along the circumference of each of the rings forming the masking wheel. Note that when no pattern is being provided, i.e., when only a continuous stripe is being deposited it is not necessary to provide indexing holes on the strip nor teeth 21 on the rings of the masking wheel. FIG. 7D shows a mask which also includes indexing holes 150. The mask of FIG. 7D also includes apertures or perforations 152 which define the pattern to be deposited upon the workpiece strip 20 of FIG. 7A. When these two strips are rotated over the masking wheel 134 the teeth or cogs 146 extend through the indexing holes of both the workpiece and masking stripe to prevent any misalignment or relative movement of the two strips. This indexing arrangement insures that the masking and workpiece strips will be accurately aligned and positioned with respect to each other.

FIG. 7E illustrates the workpiece strip 20 after it has passed along with the mask 138, over the masking wheel 134 and after the deposition of material on the strip. As may be seen, the workpiece strip 20 now has a series of dots 154 thereon corresponding to the pattern 152 on the mask 138.

FIG. 7F shows the workpiece strip 20 after the stamping operation in lead frame manufacturing. After the stamping operation the lead frame comprises a series of conducting legs 156 having tips which are coated with the deposited material 158 in the manner described herein.

While the indexing arrangement described herein is most applicable for the use of a workpiece strip in conjunction with a mask strip, it is to be understood that frequently the indexing arrangement described herein is also applicable and desirable for the type of system described in FIGS. 1 through 9. Thus, in that case, the cogs or teeth would engage indexing holes in the workpiece strip alone to insure that there is no drift of the workpiece strip as it passes over the masking wheel.

In some applications it may be desirable to provide a stripe along one edge of the strip rather than at or near the middle of the strip. This can be easily accomplished with the improved vapor deposition apparatus described herein by merely removing, prior to deposition, one of the two rings 30 or 32, depending upon which edge is to be coated. Thus, the edge to be coated will extend out past the edge of the remaining ring and will be coated.

We claim:

1. Vapor deposition apparatus for continuously depositing an evaporated material along a moving workpiece strip comprising:

a. vacuum chamber,

b.' a payout reel located within said vacuum chamber for holding an untreated roll of workpiece strip before deposition;

c. a takeup reel located within said vacuum chamber for taking up and holding the workpiece strip after deposition;

d. rotatable masking wheel over which the workpiece strip passes, said masking wheel comprising first and second independent rings which are mounted parallel to each other and are axially aligned and wherein said rings are axially adjustable for varying the gap between said rings, said gap defining the maximum width of material deposited on said workpiece strip;

e. a source of evaporated material to be deposited on said workpiece strip, said source being located within the interior of said masking wheel; and

f. means for transporting said workpiece strip from said payout reel over said rotatable masking wheel for deposition, and onto said takeup reel.

2. Vapor deposition apparatus as in claim 1 including a circular shield located concentrically within said masking wheel, said shield including an opening extending circumferentially around said shield and aligned to allow evaporated material to pass through said opening and through said gap of said masking wheel, and to block substantially all of the remaining evaporated material.

3. Vapor deposition apparatus as in claim 2 wherein each of said rings includes a plurality of indexing teeth located around the circumference thereof, and wherein said indexing teeth engage index holes provided along the edges of the workpiece strip to align the same during deposition.

4. Vapor deposition apparatus as in claim 3 including an additional payoff and takeup reel, said additional reels supporting a mask strip which is passed along said masking wheel between said workpiece strip and said masking wheel, said mask strip including periodic perforations which define a pattern to be deposited on said workpiece strip, and said mask stripadditionally including indexing holes for cooperation with said indexing teeth.

5. In a vapor deposition apparatus wherein a strip of workpiece material is passed over a rotatable masking wheel within a vacuum environment and .wherein a second material is evaporated within said masking wheel and deposited on said strip as it passes along said masking wheel, and wherein said improvement comprises a masking wheel comprisingat least first and second independent rings which are mounted parallel to each other and axially aligned, and which are axially adjustable for altering the gap between said rings, said gap defining the maximum width of material deposited on said strip.

6. Vapor deposition apparatus as in claim 5 including a circular shield located concentrically within said masking wheel, said shield including an opening extending circumferentially around said shield and aligned to allow evaporated material to pass through said opening and through said gap of said masking wheel, and to block substantially all of the remaining evaporated material.

7. Vapor deposition apparatus as in claim 6 wherein each of said rings includes a plurality of indexing teeth located around the circumference thereof, and wherein said indexing teeth engage index holes provided along the edges of the workpiece strip to align the same during deposition.

8. Vapor deposition apparatus as in claim 7 including an additional payoff and takeup reel, said additional reels supporting a mask strip which is passed along said masking wheel between said workpiece strip and said masking wheel, said mask strip including periodic perforations which define a pattern to be deposited on said workpiece strip, and said mask strip additionally including indexing holes for cooperation with said indexing teeth.

9. Vapor deposition apparatus as in claim 5 wherein said masking wheel comprises N+l rings having N-l gaps between said rings for depositing N-l stripes on said workpiece strip.

10. Vapor deposition apparatus for selectively coating a workpiece strip comprising:

a. a rotatable masking wheel comprising at least two independent parallel, axially aligned rings which are axially adjustable whereby to form adjustable slotted means for defining the maximum width of material to be deposited on said workpiece strip;

b. means for passing said workpiece strip over said slotted means;

c. means for passing a masking strip along with said workpiece strip over said masking wheel, said masking strip being located between said workpiece strip and said slotted means and wherein said masking strip includes perforations thereon defining patterns to be deposited on said workpiece strip;

d. indexing means associated with said slotted means and cooperating with said workpiece strip and said masking strip for aligning said workpiece strip and said masking strip during deposition; and

e. means for directing a stream of evaporated material through said slotted means and masking strip for deposition upon said workpiece strip.

11. Vapor deposition apparatus as in claim 10 wherein said indexing means comprises indexing holes located along the edges of said workpiece and mask strips, and index teeth associated with said slotted means for cooperating with said indexing holes during deposition.

UNITE STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,735,728 Dated May 29, 1975 Inventofls) John Frederick Krumme et a1 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shownvbelow:

On the cover sheet under "Attorney" "Karl A. Limback" should read Karl A. L'imbach Column 1, line62 "ships" should read chips Signed and sealed this 8th day of January 1974.

(SEAL) Arrest:

EDWARD M.FLETCHER,JR. RENE D. TEGTMEYER Attesting Officer Acting Commissioner of Patents FORM FED-1050 (10-69) usc g 5o q.p59

1* us aovzaumzm' PRINTING OFFICE: 190 o-su-au, 

1. Vapor deposition apparatus for continuously depositing an evaporated material along a moving workpiece strip comprising: a. vacuum chamber; b. a payout reel located within said vacuum chamber for holding an untreated roll of workpiece strip before deposition; c. a takeup reel located within said vacuum chamber for taking up and holding the workpiece strip after deposition; d. rotatable masking wheel over which the workpiece strip passes, said masking wheel comprising first and second independent rings which are mounted parallel to each other and are axially aligned and wherein said rings are axially adjustable for varying the gap between said rings, said gap defining the maximum width of material deposited on said workpiece strip; e. a source of evaporated material to be deposited on said workpiece strip, said source being located within the interior of said masking wheel; and f. means for transporting said workpiece strip from said payout reel over said rotatable masking wheel for deposition, and onto said takeup reel.
 2. Vapor deposition apparatus as in claim 1 including a circular shield located concentrically within said masking wheel, said shield including an opening extending circumferentially around said shield and aligned to allow evaporated material to pass through said opening and through said gap of said masking wheel, and to block substantially all of the remaining evaporated material.
 3. Vapor deposition apparatus as in claim 2 wherein each of said rings includes a plurality of indexing teeth located around the circumference thereof, and wherein said indexing teeth engage index holes provided along the edges of the workpiece Strip to align the same during deposition.
 4. Vapor deposition apparatus as in claim 3 including an additional payoff and takeup reel, said additional reels supporting a mask strip which is passed along said masking wheel between said workpiece strip and said masking wheel, said mask strip including periodic perforations which define a pattern to be deposited on said workpiece strip, and said mask strip additionally including indexing holes for cooperation with said indexing teeth.
 5. In a vapor deposition apparatus wherein a strip of workpiece material is passed over a rotatable masking wheel within a vacuum environment and wherein a second material is evaporated within said masking wheel and deposited on said strip as it passes along said masking wheel, and wherein said improvement comprises a masking wheel comprising at least first and second independent rings which are mounted parallel to each other and axially aligned, and which are axially adjustable for altering the gap between said rings, said gap defining the maximum width of material deposited on said strip.
 6. Vapor deposition apparatus as in claim 5 including a circular shield located concentrically within said masking wheel, said shield including an opening extending circumferentially around said shield and aligned to allow evaporated material to pass through said opening and through said gap of said masking wheel, and to block substantially all of the remaining evaporated material.
 7. Vapor deposition apparatus as in claim 6 wherein each of said rings includes a plurality of indexing teeth located around the circumference thereof, and wherein said indexing teeth engage index holes provided along the edges of the workpiece strip to align the same during deposition.
 8. Vapor deposition apparatus as in claim 7 including an additional payoff and takeup reel, said additional reels supporting a mask strip which is passed along said masking wheel between said workpiece strip and said masking wheel, said mask strip including periodic perforations which define a pattern to be deposited on said workpiece strip, and said mask strip additionally including indexing holes for cooperation with said indexing teeth.
 9. Vapor deposition apparatus as in claim 5 wherein said masking wheel comprises N+1 rings having N-1 gaps between said rings for depositing N-1 stripes on said workpiece strip.
 10. Vapor deposition apparatus for selectively coating a workpiece strip comprising: a. a rotatable masking wheel comprising at least two independent parallel, axially aligned rings which are axially adjustable whereby to form adjustable slotted means for defining the maximum width of material to be deposited on said workpiece strip; b. means for passing said workpiece strip over said slotted means; c. means for passing a masking strip along with said workpiece strip over said masking wheel, said masking strip being located between said workpiece strip and said slotted means and wherein said masking strip includes perforations thereon defining patterns to be deposited on said workpiece strip; d. indexing means associated with said slotted means and cooperating with said workpiece strip and said masking strip for aligning said workpiece strip and said masking strip during deposition; and e. means for directing a stream of evaporated material through said slotted means and masking strip for deposition upon said workpiece strip.
 11. Vapor deposition apparatus as in claim 10 wherein said indexing means comprises indexing holes located along the edges of said workpiece and mask strips, and index teeth associated with said slotted means for cooperating with said indexing holes during deposition. 